Judges dealing with sensitive issues – including child custody – in the family courts have had hate mail sent to their homes, been physically attacked and been victims of attempted assaults in court buildings, according to information obtained by the Guardian.

In the 12 months up to January this year, 26 incidents were recorded, including one direct threat to life and three physical attacks. The Guardian understands – from another source – that one of these involved a judge who required hospital attention after being knocked to the floor and beaten by a parent over whose case she was presiding.

Despite the HM Courts & Tribunals Service (HMCTS) saying it had "a robust security and safety system to protect court users and the judiciary", families whose cases were being heard were able to throw chairs and water at judges. Other judges reported being spat at. Six received abusive or threatening correspondence.

There are likely to have been more attacks than official records reveal, however. Judges said they were reluctant to speak out publicly about the violence they encountered in the courts or make official complaints for fear of increasing the threats.

"It is part of judges feeling exposed and unprotected, I suppose," said one judge speaking anonymously. "We all have what is meant to be a hotline to the police in case of trouble but I'm not sure it works. A judge told me he rang it and absolutely nothing happened. It was not a hotline at all in his experience.

"There is also a problem of people putting horrible stuff on the net, including threats. Judges have made orders for them to stop but I don't know if they do."

A number of freedom of information requests submitted by the Guardian revealed that at least five district judges have received threatening correspondence in the past year related to hearings they have presided over. One letter was sent to a judge's home address, three messages were posted on social media sites and one abusive email was received – the last two incidents suggesting the writers were able to discover and access the judges' private email addresses and social media pages, such as Facebook.

Family courts deal with parental disputes over the upbringing of children; local authority intervention to protect children; decrees relating to divorce; financial support for children after divorce or relationship breakdown; some aspects of domestic violence and adoption.

Another judge told of an incident in which a judgment was secretly taped. "A man who promised me he was not recording the hearing did so, then posted the recording online," said the judge.

"His page was full of stuff about a judge, not nice, not me. I warned that judge and made a lot of it because I thought he was a threat. A high court judge made orders about it."

Any subsequent breaking of a court order could lead to the offender being sent to prison or fined.

The HMCTS refused the Guardian access to reports regarding the incidents and said it was not known whether any of the perpetrators' actions were reported to the police or how many cases went on to criminal proceedings.

But, said another judge: "The trouble is that no one will do anything about it. Clearly, that is not right and in my view the Ministry of Justice or the attorney general should do something but I'm not aware of it happening. If the case is still ongoing, the judge running the case can deal with it, but if the case is over, and it is often when a final decision is made that these things happen, then in my experience nothing happens."

However, another judge said: "For over a decade, I have been interfering in people's lives in the most drastic sense and I've not been seriously abused or threatened. Perhaps that is surprising?"

The HMCTS said it took security within courts extremely seriously and had "a robust security and safety system to protect court users and the judiciary".

"This system includes mandatory bag searches, metal detectors and surveillance cameras, as well as court security officers who have legislative powers to protect all those in the court building. The powers of the court security officers include the ability to restrain and remove people from the building should there be a need," it said.

"Our security system is continually monitored to ensure that it is effective and proportionate and mitigates against the risks faced."